A. Field of the Invention
This invention pertains to an improved method of plating niobium containing alloy material. In particular, this invention relates to a method of improving the plating properties of magnetic alloy materials containing niobium such that there is a high permanence of bond between an electric contact material plated to the surface of the niobium containing material. Still further, the instant invention relates to a method of cleaning niobium containing alloy materials prior to plating in order to eliminate niobium oxide formed on the surface of the material during the annealing of the alloy material in a reducing atmosphere.
B. Prior Art
It is known in the prior art that a semi-hard magnetic material maybe prepared by adding a small amount of niobium (in order of 1 to several percent) to parmalloy consisting of nickel and iron. It is also known in the prior art that such materials prepared in this matter are usable for producing wire memory elements and reed relay elements, particularly, latching reed relay elements. Such semi-hard magnetic materials have been found to have a high stiffness which may be utilized to form switch devices or connector elements. In these cases, the materials made of the semi-hard magnetic materials are usually plated with metals suitable for contact materials such as gold, silver, rhodium and other like elements as well as combinations thereof.
However, in such prior art, it has been difficult to place the semi-hard magnetic material containing niobium with sufficient binding permanence of the plated metal layer. In some prior cases, the semi-hard magnetic materials have usually been annealed at a high temperature in a hydrogen atmosphere. The annealing process has been found to result in the formation of a niobium oxide layer on the suface of the material. The niobium oxide layer has been found to provide a poor bond of the metal to the material surface.
In some prior cases, the reed elements of reed switch devices have been prepared from 52-alloy consisting of 52 parts by weight of nickel and 48 parts by weight of iron. In some prior processes, the reed element is annealed at a temperature of about 700.degree. C for approximately 1 hour in a hydrogen atmosphere and the annealed element is then plated. Additionally, the reed element has in some prior cases been prepared from other semi-hard magnetic materials such as nibcolloy, consisting of 85 parts by weight of cobalt, 12 parts by weight of iron and 3 parts by weight of niobium. Due to the presence of the small amount of niobium, the nibcolloy has, in some cases, been found to have poor plating properties. This has been found true even when the nibcolloy material is annealed in a hydrogen atmosphere and thereafter plated under the same conditions as that of the 52-alloy. In such cases, it has been found that the metal layer plated unto the nibcolloy article has a high peeling tendency.
In contradistinction to such cases, other prior art alloys containing no niobium such as 52-alloy and an alloy consisting of 85 parts by way of cobalt and 15 parts by way of iron, have been found to have no peeling tendency even if they are plated after annealing under the same condition as that described for the nibcolloy. Therefore, it has been found in the prior processes that the high peeling tendency of the metal layer plated onto the nibcolloy material is derived from the presence of niobium therein. That is, a portion of niobium located on the surface of the material is converted to niobium oxide during the annealing at a high temperature. The niobium oxide layer thus formed results in a peeling tendency and a poor fixedness of the metal layer plated thereon.
It is known in the prior art that niobium oxide is soluble in hot aqueous alkali solution. However, such prior processes and systems are not believed to show that the treatment of hot aqueous alkali solutions to niobium containing magnetic alloy material improves the plating properties of such materials after the materials have been annealed in a hydrogen atmosphere.
Additionally, it is known in the prior art that when niobium pentoxide is reduced by hydrogen, lower oxides of niobium may be obtained. However, it is not believed that such prior systems and processes provide for the improved method of plating alloy materials consisting of niobium, cobalt and iron through annealing of the alloy materials in a predetermined atmosphere, and then following by immersing the alloy material in an aqueous solution of sodium hydroxide prior to the plating process as well hereinafter be described.